Sparking in dynamo electric machines



(No Model.)

E. II. MA'I'IIEE..

DEVICE EUR PREVENTING SPARKING IN DYNAMO ELECTRIC MACHINES. N0. 321,990. Patented July 14, 1885.

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RICHARD H. MATHER, OF VINDSOR, CONNECTICUT.

DEVICE FOR PREVENTING SPARKING IN DYNAMO-ELECTRIC MACHINES.

.CPECIFICATIQN forming part of Letters Patent No. 321,990, dated July la, 1885.

Application (led July l, 1884.

To @ZZ whom, it may concern:

Be it known that I, RicHARD H. MA'rHnraa citizen of the United States, residing at Windsor, in the count-y of Hartford and State of Con necticut, haveinvented certain new and useful Improvements in Devices for Preventing Sparking in Dynamo-Electric'Machines5 and I do declare the following to be a full, clear, and exact description of the invcntion,such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawing, and to the letters and iigures of reference marked thereon, which form a part of this specification.

My invention relates to dynamo-electricmachines in a broad sense, including not only all machines for convert-ing energy in the form of dynamical power into energy in the forni of electric currents by the rotation of conductors in a magnetic field; but also those electrical machines which, having a similar construction but operating in the reverse manner, are known as electric motors.7

The object of my invention is to provide a simple, effective, and inexpensive means of preventing the occurrence in such machines of the phenomenon known as sparkingf7 and my device for the accomplishment of this object consists of a magnet or a number of magnets, as the case may be, in addition to or in extension of the' field-magnet of such a machine, which device may appro priately be termed a neutralizing-magnet," from the circumstance that in tlie operation of my invention this magnet has an inductive effeet upon the armature-core the reverse of that ofthe armature-current. This magnet neither increases nor diminishes the useful external current of the machine, but has for its sole purpose the production of a current in those coils of the armature which are for the time being short-circuited by the brush or brushes of the comniutator. I proceed to point out the best mode of applying my invention.

The accompanying drawing is a diagrammatic representation of a dynaino-electric machine embodying my invention. For the mere purpose of illustration and explanation, I

(No model.)

have chosen 'for tlie drawing a shunt-dynam0,7 socalled, having a drum-armature.

In the drawing, F is the held-magnet, the particular form of which is unimportant in this connection. The north and south poles of the iield-inagnet are lettered, respectively, N and S.

A is the revolving armature, provided with commutator C and brushes b and b, as shown, while a is the north pole of the armature or armature core as magnetized by the armature current.

P is the neutralizing-niagnct, which is the principal feature of my invention, and consists of a core of soft iron wound as an electro-magnet, having north and south poles lettered, respectively, N and S. This core should, preferably, bein the forni of a thin and narrow plate, an edge view of which is seen in the drawing, and may be suspended perpendiciilarly between the arms of the ield-magnet. The same should be placed iii a fixed position, such that its north pole,N,sliall be close to the armature at or near the middle point between the poles N and S of the field-magnet; or, which is the same thing, should be tixed opposie and near the theoretical neutral. point of the armature A. The best attachment of the neutralizing-magnet is by bolting the same to the iield-inagiiet in the position mentioned, as shown in the drawing. The neutralizingmagnet I is of sufficient size and is wound to a sufficient degree of electro magnetic etliciency to insure the control of the armature thereby in the manner hereinafter describedthat is to say, t-lie neutralizing-magnet is constructed to have a considerably higher niagnetic efficiency than the armature A.

The coil of the neutralizing-magnet is by preference to be placed in the armature-circuit, as distinguished from the iield-inagnet circuit, in order that the magnetization ofthe neutralizingmagnet may vary with the current in the former circuit and not with the current in the latter circuit in the manner hereinafter explained.

As it is unnecessary, in viewof the mode of operation of this invention, to set the brushes forward in generators or backward in motors, in the manner which hasheretofore been prac- ICO tieed for the purpose of preventing sparking, the brushes Z) and b are placed in such positions as to make contacts with the commutator in a perpendicular line through the neutral points of the armature.

rI`he remaining features of' construction and the appropriate connection of the several parts ofthe dynamo embodying my invention will sufficiently appear from the drawing, and from the mode ol." operation as hereinafter cxplained.

It is a well-known fact that in dynamoelcctricgenerators heretofore constructed,andhaving the Pacinotti or Siemens system of armature-coil connections, it has been necessary to set the brushes forward, and in dynamo-electric motors of like construction to set the brushes backward upon the commutator, in order to prevent sparking, which adjustment ofthe brushes, whether manual or automatic, has nevertheless been not entirely efficacious to produce that result. Also, it has been necessary that the adjustment of the brushes should be variable, on account ot' the variations in the absolute strength of the field magnet, or in the relative strength of the fieldmagnet as compared with the armature due to wf'a'riations in the electro-motiveiorce or current of the machine; for, by reason of such variations,the neutral point or points in the armature have been movable and incapable of being fixed by the brushes.

The mode ot' operation of my invention is as follows: then the machine is in operation the electric current passes through the armature and through the main and shunt circuits in the courses and directions indicated in the drawings, whereby the neutralizingmagnet I? is energized as an electro magnet in a degree dependent upon and varying with the strength ofthe current through the armature, which dependence and variation follow from the above-described location ot' the neutralizing-magnet coil in the main circuit. During the operation of'l the machine,therefore, the neutralming-magnet, whose north pole is by said construction near and opposite the theoretical neutral point ofthe armature, causes or tends to cause a reversal in the direction of' the current traversing` those coils of the armature which are for the time being passing` directly under that magnet, and this magnetic infinence or tendency to cause reversal automatically varies in strength according to the varying strength ofthe current so to be reversed for the reason before stated-namely, the inclusion ofthe neutralizing-magnet coil in the armaturecircuit. Alike result has hitherto been accomplished by throwing the brushes over into such a position that those coils of the armature which would otherwise produce sparking are brought under the direct magnetic influence of the field-magnet.

In the case of a dynamo having a ring-armature the neutralizing-magnet will affect in the manner described those armature-coils only which are directly opposite and adjacent thereto; hence it is necessary in dynamos of that class to place asecond neutralizing magnet upon the opposite side of the armature; and in the case of dynamos having multiple poles additional neutralizing magnets are necessary, also, I do not confine my invention to a dynamo-electric machine having a neutralizing-magnet in the main circuit with the armature; for the neutralizingmagnet may be placed in a shunt, or in an independent circuit, or may even be a strong permanent magnet.

By means of my invention any strength of' current which the armature is capable of carrying can be taken oft' from the cominutator by the brushes without sparking.

I claim as my invention and desire to secure by Letters Patentl. Adynamo-electric machine provided with a magnet whose north or south pole is adjacent to the like pole of the armature, substantially as and for the purpose specified.

2. In a dynamo-electric machine, a sparkpreventing device consisting ot'an electro-magnet whose helix is located in the main circuit ofthe machine, and one of whose poles is adjacent to the like pole of the armature, substantially as set forth.

3. In a dynamo-electric machine, a sparkpreventing device consisting ofan electro-magnet which is attached to the field-magnet, is located in the main eircnit,and has one of its poles adjacent to the like pole of the armature, substantially in the manner and for the purpose specified.v

el. In a dynamo-electric machine, an electro-magnet in circuit with the armature and having one of its poles adjacent to the like pole of such armature, sul'istantially in the manner and for the purpose specified.

5. In a dynamo-electric machine, a device to prevent sparking,consisting of one or more magnets so placed that the neutral point or poi nts of the armature of such machine shall be within the magnetic field thereof7 substantially as and for the purpose specified.

6. In a dynamo-electric machine, a device to prevent sparking,consisting of'l an electroniagnet in circuit with the armature and so placed relatively to t-hc armature that one of the poles of such magnet and the like pole of' the armatureshall be next to each other, substantially as specified.

Intestimony whereofI affix my signature in presence of two witnesses.

RICHARD H. MATHER.

Vitnesses:

Irma-inn EDDY, RA Lrn H. PARK.

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